OK, so you are after a flat top inner with a tarp on top.
No, I am not aware of anything like that.
I suggest you make yourself a full scale mock up of that design, doing that it may become a bit more obvious why it isn't all that efficient for both space and use of fabric.
On top of that it would be difficult to prevent the inner banging against the fly in the wind.
(I could be wrong...)



the above photo is just to give you an idea of what I mean about full scale mock up.
That particular set up I did to demonstrate how much dead space there is inside a 4 sided pyramid tent (about 40Sq feet in that one...)